<!doctype html>
<html lang="zh-cn">
<head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="lib/css/bootstrap.css">

    <title>Bootstrap栅格系统</title>

    <style>
        .container > .row > div:nth-child(1) {
            background-color: pink;
        }

        .container > .row > div:nth-child(2) {
            background-color: red;
        }

        .container > .row > div:nth-child(3) {
            background-color: blue;
        }

    </style>
</head>
<body>
<div class="container">
    <div class="row">
        <div class="col-xl-5">三分之一空间占位</div>
        <div class="col-xl-5">三分之一空间占位</div>
        <div class="col-xl-2">三分之一空间占位</div>
    </div>
</div>

<!-- Optional JavaScript -->
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src="lib/js/jquery-3.4.1.js"></script>
<script src="lib/js/popper-2.4.4.js"></script>
<script src="lib/js/bootstrap.js"></script>
</body>
</html>